Polonium, Novichok and now dart frog poison: the finding that Russian opposition leader Alexei Navalny was killed with a rare toxin has revived the specter of Moscow¡¯s use of poisons against opponents ¡ª a hallmark of its secret services, according to experts.

The neurotoxin epibatidine, found in Ecuadoran frogs, was identified in laboratory analyses of samples from Navalny¡¯s body, the British, Swedish, French, German and Dutch governments said in a joint statement released on Saturday at the Munich Security Conference.

¡°Only the Russian state had the means, motive and opportunity to deploy this lethal toxin,¡± said Britain¡¯s Foreign Office, with the joint statement pointing to Russia as the prime suspect.